Crosschaining is running the largest rings together or smallest rings together so that the chain crosses from one side to the other between the cranks and the cassette. It sounds like the chain is jumping under load. Did you get the bike at a shop? If so take it back and have them take a look at it. They'll be able to tell you a lot more by looking at it than we can over the internet.

Crosschaining is running the largest rings together or smallest rings together so that the chain crosses from one side to the other between the cranks and the cassette. It sounds like the chain is jumping under load. Did you get the bike at a shop? If so take it back and have them take a look at it. They'll be able to tell you a lot more by looking at it than we can over the internet.

thanks, but yeah, thats what i have been doing. I guess when you set the 1 2 or 3 gear, you have to have it in a specific gear in the rear huh? i'll learn that stuff myself today. thanks a lot for the explaination streetlight!

I may get jumped on for bad advice but my understanding is that if you are in your granny gear up front you'd want to be using about the 5 largest cogs in the back, in your second ring (assuming a triple) you should be able to use all 8 or 9, and in your largest front ring use the ~5 smallest rear rings. The point is to not have a chainline that is farther off than the derailleur can handle.